1. Technical Field
The present invention relates to an ink composition suitable for ink jet recording, in particular, an ink composition with superior ozone resistance, bronzing resistance and coloring property, an ink jet recording method using the same and a recorded material recorded by the recording method.
2. Related Art
Ink jet recording is a method for recording text or images (hereinafter, simply referred to as an “image”) on the surface of a recording medium by ejecting droplets of an ink composition from a fine nozzle. As the ink jet recording method, a method for recording text or an image on the surface of a recording medium by converting electric signals into mechanical signals using an electrostrictive device and intermittently ejecting an ink composition stored in a nozzle head, a method for recording text or an image on the surface of a recording medium by rapidly heating a region immediately adjacent to the ejection part to foam an ink composition stored in a nozzle head and intermittently ejecting the ink composition through volume expansion due to the foam or the like is practically applied.
In addition, as ink compositions for ink jet recording, solutions of a variety of dyes in water or an organic solvent, or a mixture thereof are generally used in terms of safety or printing properties. Taking into consideration various properties, ink compositions for ink jet recording are required to conform to more stringent conditions, as compared to ink compositions for writing implements such as fountain pens or ball pens.
In particular, recently, ink jet printers have often been used for producing advertising prints, and there is a demand for more stringent requirements, when color images are formed using a plurality of ink compositions.
The reason is that, when there is even one color with a low coloring property in color images formed using the plurality of ink compositions, the overall color balance deteriorates due to the color in the image and high-quality images cannot be thus obtained.
In an ink composition (in particular, an ink composition employing a metal phthalocyanine dye as a coloring material), a red phenomenon (hereinafter, referred to as a “bronzing phenomenon”) may be observed in a region where high-duty printing such as beta printing (fill printing) is performed. In this case, the overall color balance of images is imbalanced and image quality is thus deteriorated. Accordingly, improvement of the composition is required.
In addition, recently, gloss paper has commonly been used as a recording medium having a texture with a tone like a photo. However, a specific color causes bronzing, leading to imbalance of gloss texture on the surface of printed materials and thus considerable deterioration in the texture of images. In terms of maintenance of the overall gloss texture of images, there is a strong requirement for improvement of the composition.
In addition, ink compositions which exhibit superior light resistance and gas resistance, when printed materials formed using the ink compositions may be mounted indoors as well as outdoors and are thus exposed to sunlight as well as a variety of light or the external atmosphere (ozone, nitrogen oxide, sulfur oxide or the like), have been developed. In particular, cyan ink compositions in which gas resistance is improved in terms of intrinsic properties of the dye, exhibit a remarkable bronzing phenomenon. Improvement of the ink compositions is required.
In addition, it is known that, when the ink composition for ink jet recording which uses a dye having a lack of solubility in water is printed on highly acidic recording media, a so-called “bronzing phenomenon” occurs.
As this method for solving the problem, addition of alcohol amines such as a pH adjuster or improvement of permeation strength into paper is generally performed. Basically, the bronzing phenomenon is caused by an ink composition being dried on the surface of paper and the dye thus being crystallized. This method is effective in that solubility is improved to prevent crystallization or the ink composition permeates into paper before crystallization. However, the former is not a perfect solution, since pH easily increases to about 11 by addition, a printer nozzle is corroded, and the method may have an effect on humans. The latter is not a perfect solution; since when there is an excessive increase in permeability, another printing quality, a so-called “bleeding phenomenon” or the like, is deteriorated.
As an alternative to these methods to solve these problems, an ink composition containing a 2-oxo-oxazolidone or 1,3-bis(β-hydroxyethyl)urea is suggested (for example, see JP-A-6-25575).
In addition, an ink composition containing a basic amino acid to solve the problems is suggested (for example, see JP-A-7-228810).
In addition, an ink composition containing a phthalocyanine compound with ozone resistance is suggested (for example, see JP-A-2004-263155).
However, as a result of a variety of investigations and research, the present inventors found that an ink composition exhibits superior ozone resistance and bronzing resistance, but does not impart high printing intensity in spite of using the solutions described above.